Unit air filter latch



June 1963 w. J. HAGENDOORN 3,093,401

UNIT AIR FILTER LATCH Filed Dec. 19. 1960 INVENTOR. WILLEM J. HAGENDOQRNATTORNEY United States This invention relates to unit air filterlatches.

Unit air filter cells or panels are normally mounted within an auxiliaryframe which is permanently installed to extend across an air stream. Theauxiliary frame has an unobstructed front opening and a marginallyflanged rear opening, and latch means mounted on the frame are used toreleasably hold the filter cell within the frame. The latch means in acell-latching-pos-ition normally engages the front margin of the cell attwo or more points and presses the cell rearwardly to effect an airsealing engagement of the rear margin of the cell against the rearflange of the frame.

Many prior latches have not been completely acceptable for one reason oranother. A deficiency of certain latches has been that they projectforwardly from the frame so that increased shipping and storage space isrequired. Also the projecting latches are subjected to the possibilityof damage during handling and storage. Another deficiency of certainlatch arrangements is that the latches have relatively small contactareas which concentrate the rearward pressure on the filter cell at afew points only instead of distributing the force over a substantialpart of the filter cell margin. With certain filter cells, such as thoseemploying pasteboard channel margins, the concentrated pressure causesthe margin to so deform and how that the air seal between frame and cellis lost.

An object of this invention is to provide a relatively inexpensive,simple, easily operated latch which: does not have rigidly mountedforwardly projecting parts; may be released to a position permittingunobstructed removal of a filter cell; does not deform the margins of afilter cell to an extent that the air seal between frame and cell islost; and which satisfies other known requirements for filter latches.

The invention will be described in connection with the accompanyingdrawing illustrating the principles of the invention incorporated in oneembodiment by way of example, and wherein:

. FIGURE 1 is a partly broken front face view of a unit filter cellmounted in an auxiliary frame provided with a latch constructed inaccordance with the present invention;

FIGURE 2 is a fragmentary isometric view of an auxiliary frame wallfitted with the latch, this view showing a filter cell margin in theframe and the latch in a celllatching-position but not locked in thatposition;

FIGURE 3 is a sectional view taken along the line 3-3 of FIGURE 1 withthe latch in a cell-latching-position; and,

FIGURE 4 is a sectional view similar to FIGURE 3 but illustrating thelatch fully retracted to a cell-releasingposition.

The metal auxiliary frame has perimetric side walls 2 defining a frontunobstructed opening, and an inwardly directed rear flange 4 definingthe rear opening. On the front face of flange 4, felt 6 or othersuitable material is adhesively secured so that when an air filter panelor cell 8 is fitted within the frame the rear face of a channelshapedmargin 10 lies against the felt 6. The filter cell is pressed rearwardlyand held within the frame by the latching means engaging the front faceof the margin 10 along at least two sides of the cell.

The latching means of the invention are propably best understood in ageneral way in connection with FIGURE 2. At least two of the side wallsof the auxiliary frame are att Patented June 11, 1963 ice provided withidentical latches in the form of somewhat bail-shaped wire arms havingan elongate straight portion or bight 12 adapted to press against thefront face of the filter cell margin when the latch is incell-engaging-position, and having ends 14 which are axially offsetrelative to the bight and each of which is pivotally secured by a hingestrap 16 welded to the auxiliary frame wall.

The bight 12 of each latch carries an L-shaped clip having a leg portion18 and a base portion 20. The toe of the base portion 20 is rolled toform a sleeve 22 encircling the bight 12 in such fashion that the clipmay be both slid axially along, and rotated about, the bight. Near thefront edge of the auxiliary frame wall 2, a tongue-like keeper elementor detent is secured. The detent includes a base portion 24 welded tothe inner face of the wall, and an offset portion 26 spaced away fromand extending along the wall so that a passage having one open end isformed along the wall. When the clip is moved into engagement with thedetent so that the leg 18 is received between the offset portion 26 andthe wall, the bail latch is locked in a cell-engaging-position. When theleg 18 is moved out of the passage, the bail latch is free to be movedout of a cellengaging-position. The bail is preferably made of rod orwire material which does not appreciably yield in normal service.Consequently, when the bail is locked in position, the filter cell ispressed rearwardly by substantially the entire length of the bight 12with the bight being held in position at both ends and by the clip. I

FIGURE 3 illustrates the position of the latching means relative to theframe wall and cell margin in a cell-engaging-position. In this case thelatch bail projects inwardly and somewhat rearwardly from the frame wallwith the bight 12 pressing along the front face of the cell margin. Itwill be appreciated from this view that, in accordance with theinvention, the clip is so dimensioned, relative to the swinging radiusof the bail, that the leg 13 of the clip can be received behind thedetent only when the bail is in the proper cell-engaging-position. Thatis, if the bail is swung past a correct position the clip will be tiltedwith its leg 18 out of the plane in which it must lie to be received bythe detent. Conversely, if the ball is not swung far enough toward acell-engaging-position the base portion 20 will not be long enough sothat the leg 18 can be received by the detent. Thus, the latch assemblyis so made that the front marginal face of the cell is firmly engagedand possibly flexed by the bail when it is in the correctcell-engaging-position. This arrangement not only insures a tight ai-rseal between the flange 4- and the rear face of the cell margin, butalso avoids any guesswork as to when the ball is in a proper latchingposition.

FIGURE 4 illustrates the latching means in a retracted positionpermitting the removal of the cell. In this case the bail has been swungforwardly and outwardly until it lies closely against the auxiliaryframe wall 2. During this cell-release-operation, the clip has been sorotated that it projects laterally out of the front face of the frame topermit the unobstructed removal of the cell. To the end that thislateral projection of the clip out of the frame is possible, the bail isdimensioned and hinged, relative to the front edge of the auxiliaryframe, so that its swinging radius is sufiicient to carry the bight 12of the the bail to a position relative to the front edge of the framethat the clip can be rotated to a position where it does not obstructthe front opening of the frame.

It is also noted that the detent is positioned with its forward edgespaced rearwardly from the forward edge of the auxiliary frame. This isdone so that as the :bail is swung to its cell-releasing-position, thebail will clear the detent and thereby permit the bail to lie closelyagainst the frame wall. I

It will be appreciated that the hinge strap 16 and the detent tongue 26need not be separate parts secured to 3 the wall 2, but instead may beintegral with but struck out from the frame wall.

For modifying auxiliary frames in service but having unsatisfactorylatch means, the latch assembly including the hinges, bail, clip, anddetent may all be mounted on an integral base member (not shown) whichmay in turn be secured to a frame in service.

The auxiliary frame may be shipped with the latch locked in acell-engaging-position even though the cell itself is shippedseparately. Or if the latch is not locked in a cell-engaging-position,the latch may be swung dovmwardly with the clip toward the rear of theframe so that no part of the latch means projects out of the frame.

While the invention has been described in connection with a filter cellhaving a frame around the edges, it will be appreciated that the latchmay he used with a filter pad not enclosed by a frame if a suitableopen-work grid is provided for the front and rear faces of the pad.

The invention claimed is:

1. An improvement in latches for releasably retaining an air filter cellwithin a forwardly open auxiliary frame having a marginal sealing flangealong its rear, comprising: a bail-shaped latch having an elongate bightand axially ofiFset ends pivotally secured to a wall of said frame topermit swinging movement of said latch from a cellreleasing-position inwhich the bight of said latch lies closely adjacent said wall permittingremoval and insertion of a cell, to a cell-latching-position in whichsaid bight is swung inwardly to lie in spaced relation from said wallfor engagement along a forward margin of said cell; a tongue projectinginwardly from, and extending along, said wall in spaced relation theretoto define a clip retaining slot between said wall and tongue; and latchlocking means in the form of an angular clip slidably mounted on saidbight for movement therealong to a latch locking position wherein aportion of said clip is received within said slot to retain said latchin a cell-latching-position.

2. An improvement in latches for releasably retaining an air filter cellwithin a forwardly open auxiliary frame having a marginal sealing flangealong its rear, comprising: a bail-shaped latch pivotally secured at itsends for swinging movement of the bight thereof between acellengaging-position in which said latch projects obliquely andrearwardly away from a wall of said frame to engage a margin of saidcell and a cell-releasing-position in which said latch projectsforwardly to lie closely along said wall; an angular clip having oneextremity slidably connected to said bight for movement axiallytherealong and rotation thereabout, and an opposite leg in face-to-facecontact with said wall when said latch is in cell-engagingposition; anddetent means on said wall forming a clip retaining slot therewith toreceive and retain said opposite leg for holding said latch incell-latching-position.

3. The improvement in latches of claim 2 wherein: said latch ispivotally secured along an axis, relative to the swinging radius of saidlatch and the forward edge of said frame, that said bight in acell-releasing-position lies sufficiently forward relative to saidforward edge of said frame to permit rotation of said clip to projectlaterally out of the open face of said frame.

4. The improvement in latches of claim 3 wherein: said detent means isso disposed relative to the arc through which said bight isdisplaceable, that said bight may be moved between opposite positionswithout obstruction by said detent means.

5. An improvement in latches for releasably retaining an air filter cellwithin a forwardly open auxiliary frame having a marginal sealing flangealong its rear, comprising: a wire latching arm of generally U-shapehaving an elong ate, straight bight portion extending along a major partof the length of a wall of said frame and having its ends pivotallysecured to the inner face of said frame wall so that said bight portionmoves through an are between a cell-engaging-position and acell-releasing-position; a clip of angular cross-section having oneextremity slidably and rotatably secured to said bight portion; anddetent means on the inner face of said wall and substantially centeredrelative to said bight portion for receiving said clip in interlockingrelation when said bight portion is in said cellengaging-position.

References Cited in the file of this patent UNITED STATES PATENTS

5. AN IMPROVEMENT IN LATCHES FOR RELEASABLY RETAINING AN AIR FILTER CELLWITHIN A FORWARDLY OPEN AUXILIARY FRAME HAVING A MARGINAL SEALING FLANGEALONG ITS REAR, COMPRISING: A WIRE LATCHING ARM OF GENERALLY U-SHAPEHAVING AN ELONGATE, STRAIGHT BIGHT PORTION EXTENDING ALONG A MAJOR PARTOF THE LENGTH OF A WALL OF SAID FRAME AND HAVING ITS ENDS PIVOTALLYSECURED TO THE INNER FACE OF SAID FRAME WALL SO THAT SAID BIGHT PORTIONMOVES THROUGH AN ARC BETWEEN A CELL-ENGAGING-POSITION AND ACELL-RELEASING-POSITION; A CLIP OF ANGULAR CROSS-SECTION HAVING ONEEXTREMITY SLIDABLY AND ROTATABLY SECURED TO SAID BIGHT PORTION; ANDDETENT MEANS ON THE INNER FACE OF SAID WALL AND SUBSTANTIALLY CENTEREDRELATIVE TO SAID BIGHT PORTION FOR RECEIVING SAID CLIP IN INTERLOCKINGRELATION WHEN SAID BIGHT PORTION IS IN SAID CELLENGAGING-POSITION.